Port 3642: Juxml Replication — A Ghost from the XML Era

What Port 3642 Is

Port 3642 sits in the registered ports range (1024–49151). These ports are assigned by IANA upon application — someone submits a name, a protocol, and a purpose, and IANA adds the entry to the official registry.¹

In November 2002, port 3642 was registered for both TCP and UDP under the name juxml-port, described as the "Juxml Replication port."²

The Juxml Story

"Juxml" is almost certainly a portmanteau of Java and XML — a natural construction for 2002, when XML was going to solve everything. XML databases, XML replication, XML middleware: the early 2000s produced dozens of projects built around the idea that structured markup was the universal language of distributed systems.

Juxml appears to have been one of them. It registered a port, which suggests someone had working software (or at minimum, working ambition). Then it disappeared. No documentation survives. No project page, no source code repository, no mailing list archive. Whatever Juxml was — an internal enterprise tool, an academic project, a startup that didn't make it — it left only this: a single entry in a government registry.

The port number will remain assigned to it indefinitely. IANA doesn't reclaim ports. The ghost gets to keep the room.

What You'll Find on Port 3642 Today

Almost certainly nothing related to Juxml. In practice, port 3642 today is more likely to be:

• Ephemeral traffic — operating systems use registered ports as outbound source ports when the dynamic range is exhausted
• Application-specific use — software that needed a port and picked this one because it was available in practice, even if assigned on paper
• Scanning noise — automated scanners probing for open ports

If you see traffic on port 3642 on your own machine or network, it almost certainly has nothing to do with Juxml.

How to Check What's Listening

To see if anything is bound to port 3642 on your system:

macOS / Linux:

lsof -i :3642

Windows:

netstat -ano | findstr :3642

Cross-platform (with nmap):

nmap -p 3642 localhost

If something is listening, the process name will tell you what it is. Knowing the port number alone won't help — the Juxml replication protocol is not something any living software speaks.

Why Unassigned-in-Practice Ports Matter

The registered ports range exists to prevent collisions — two applications accidentally choosing the same port number and interfering with each other. It mostly works. But the registry also contains hundreds of entries like this one: ports assigned to projects that never shipped, software that went end-of-life, or companies that no longer exist.

This creates a quiet ambiguity. Firewalls configured to block "registered services" may treat port 3642 as having a known purpose when it doesn't. Security tools may flag traffic on this port as anomalous. The registry entry creates the appearance of meaning where there is none.

The honest read: port 3642 is effectively an unassigned port wearing a name tag from 2002.